The ARM/DISARM commands correspond to two positions of a dedicated handle that also visually indicate the status of the door. An indicator lamp can confirm this status at all times.
In the disarmed position, the evacuation slide is stored in a box fixed to the internal wall of the door in the form of a tube attached to and surrounding the girt bar, the box being arranged at the bottom of the door or in some installations in the fuselage, under the door threshold. The girt bar is held parallel to the floor of the cabin by U-shaped clamps provided with releasable clips in the form of leaf springs or the like. When the handle is moved to the door armed position (ARM), the rotation movement of the handle is converted into vertical translation movement by mechanical cables—for example “push-pull” cables—to lock handles attached to the bar to jaws of integrated fittings under the threshold of the floor. Conversely, of the bar is released by a mechanism for relaxing the jaws actuated by a cable connected to an ancillary handle, for example. A visual indicator reinforced by an audible warning device advises the operator that the evacuation slide of the door that they are attempting to open is armed.
This type of solution has been described in numerous patent documents, such as U.S. Pat. Nos. 3,634,914, 4,715,562, EP 0743 246 or WO 8400786, for example.
Improvements have been proposed in order to take into account particular issues in the perilous context of emergency opening of a cabin door. For example, to prevent the untimely deployment of the evacuation slide, US patent document 2011/0139934 provides human presence sensors facing the cabin door connected to a warning device indicating such presence in the vicinity of the internal handle of the door.
Another example, referred to in the document U.S. Pat. No. 7,090,168, concerns the load supported by the girt bar attached at its ends when the evacuation slide is deployed and inflated. In order to prevent the generation of a bending moment at the centre of the bar, which might cause it to break, superposed flexible panels are provided to create a distribution of the forces from connection points on the girt bar or on the cabin floor fittings.
However, the girt bar and the locking cables of such a bar have numerous disadvantages:
the bar has a non-negligible weight and forms an obstacle to be overcome before jumping onto the evacuation slide;
anchoring the fittings under the threshold of the floor leads to accumulation of dust and other “detritus” (soil, small objects, etc.), which fouls the mechanics and can prevent correct deployment of the evacuation slide;
the transmission cables may jam or break because of the complexity of the system;
disarming can be difficult under difficult climatic conditions: frost, ice, snow, corrosion, jamming, etc.;
if it is not equipped with a “snap-action” type tensioning device, the ARM/DISARM handle can assume an intermediate position between the two command positions;
it is difficult to demount an evacuation slide in order to remount it at another door in the event of ditching.